Working With Text Files in PHP - Creating and Writing Files
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Files are flexible. They can contain text or binary data. They can contain anything from a single character to 100,000 lines of XML. It is this flexibility combined with PHP's simply file-handling functions that make files such an easy-to-use aspect of PHP.
On the last page we learnt how to open and read files. Creating and writing files is very similar –- we start with the fopen function:
Here are all of the file modes that relate to writing to a file:
- 'w' - Open for writing only; place the file pointer at the beginning of the file and truncate the file to zero length. If the file does not exist, attempt to create it.
- 'w+' - Open for reading and writing; place the file pointer at the beginning of the file and truncate the file to zero length. If the file does not exist, attempt to create it.
- 'a' - Open for writing only; place the file pointer at the end of the file. If the file does not exist, attempt to create it.
- 'a+' - Open for reading and writing; place the file pointer at the end of the file. If the file does not exist, attempt to create it.
So by simply specifying "w" as the file mode, PHP will move the file pointer to the beginning of the file and truncate (cut-down) the file to zero length if that file already exists. If it doesn't exist, here's the good part -- PHP will automatically create it for us!
So, how would we create a blank file using just the fopen command? Simple. Take a look:
<?php
$fp = fopen("newfile.file", "w") or die("Couldn't create new file");
?> That's really all there is to it. To actually output a value to the file, we need to use the fwrite function, which we will discuss now.
fwrite Fwrite simply writes the contents of a string to a file. The signature for the fwrite function looks like this:
int fwrite ( int fp, string string [, int length]) Fwrite returns the number of bytes written on success, or false if an error occurs. The first parameter is the file pointer ($fp in all of our previous examples). The second parameter is the string that you want to write to the file, and the third optional parameter is the length of the string that will be output to the file.
If we wanted to output a simple sentence to a file, then we could do it like this:
<?php
$fp = fopen("newfile.file", "w") or die("Couldn't create new file");
$numBytes = fwrite($fp, "Hello, this is some text!");
fclose($fp);
echo "Wrote $numBytes bytes to newfile.file!";
?> Newfile.file now looks like this:
The output from our PHP script shows how many bytes were written to newfile.file:
Simple, right! Now, remember that using the file mode "w" actually truncates the file before writing to it. What about if we just wanted to append some text to the bottom of the file? Which file mode would we use then? We have 2 choices:
- 'a' - Open for writing only; place the file pointer at the end of the file. If the file does not exist, attempt to create it.
- 'a+' - Open for reading and writing; place the file pointer at the end of the file. If the file does not exist, attempt to create it.
Because we are only performing write operations on the file, we will use "a" (remember that it's quicker to use a unidirectional access method instead of a bi-directional one, such as read/write).
So, to append a sentence to the bottom of newfile.file, we could use this code:
<?php
$fp = fopen("newfile.file", "a") or die("Couldn't create new file");
$numBytes = fwrite($fp, "\r\nLook, it's a brand new line!");
fclose($fp);
echo "Wrote $numBytes bytes to the end of newfile.file!";
?> Newfile.file now looks like this:
Before we continue, try experimenting with the different file modes to see how they work.
Next: File Writing in Action >>
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